1. Field of the Invention
This invention relates to metal soap compositions comprising essentially a metal soap and a chelating agent, which can easily be made up into a transparent aqueous solution.
2. Description of the Prior Art
Heretofore, any of metal soap have been scarcely soluble in water and soluble only in special oils. Thus, their application fields have been restricted to lubricants, stabilizers, water-proop agents, etc. in non-aqueous substance such as oils, synthetic resins, etc., and almost all of them have been used in the form of powder or oil solution.
On the other hand, fatty acid soaps react with calcium ion, iron ion or the like in hard water to form metal soaps which often precipitate to thereby reduce their surface active properties including washing effect; hence metal soap thus formed are avoided as scum. Accordingly, chelating agents have been usually blended into detergents, in advance, to thereby prevent formation of metal soaps.
Further, even when metal soaps are soluble in solvents, such metal soaps have a substantially low solubility and those which are soluble at low temperatures are few. For example, barium stearate is scarcely soluble in all solvents, and when added to water, it floats up like pollen, and even when it is heated under shaking for a long time, barium stearate does not mix with water at all. Further, metal soaps have a tendency that they are hydrolyzed in contact with water, and some of them are hydrolyzed even by a slight amount of water.
The inventor of this invention previously made various studies to develop the uses of metal soaps having drawbacks in respect to solubility and stability and thus having been restricted in application fields and also to elevate the performances of conventional surfactants still more. As a result, the inventor of this invention proposed a surfactant composition obtained by dissolving a metal soap in a water-soluble surfactant in a definite proportion or admixing the both in advance in a proportion in which the both are soluble in water (Japanese patent publication No. 20461/1972). Since the metal soaps in the compositions are solubilized by the effect of surfactants, the compositions exhibit various superior surface active properties by the combination of the properties of the both. On the other hand, however, such a composition requires surfactants in a relatively large proportion; hence the properties of the resulting composition are controlled considerably by the properties of surfactants. In this respect, such a composition has not always been satisfactory.
Thus, the inventor of this invention has further made strenuous studies in order to overcome the above-mentioned drawback, and as a result has found that when a chelating agent is added to a metal soap in a definite proportion, it is possible to effect solubilization of the metal soap in water, and yet no hydrolysis occurs; and the metal soap composition behaves as if it is a single surfactant and yet exhibits various superior surface active properties. The present invention has been made based on this finding.